OXYGEN ION CONDUCTORS AND THEIR TECHNOLOGICAL APPLICATIONS

The magnitudes of the oxygen fluxes through ceramic oxides incorporated in a variety of technological devices and systems are briefly surveyed, and attention is drawn to the importance of the kinetics of the associated surface exchange process. For most applications, oxygen ion conductivities greater than 10(-1) S cm-1 are required at intermediate temperatures (600-800-degrees-C). The strategies adopted to design materials with appropriate oxygen ion conductivity values are summarized with special reference to the fluorite, perovskite and related oxide structures. Finally oxygen ion order-disorder processes in highly defective perovskite (ABO3) and brownmillerite (ABO2.5) mixed conducting oxides are briefly reviewed, with emphasis upon the role of isotopic exchange-diffusion profile techniques to separate the contributions of the various charge carriers to the total conductivity.